JPH02141565A - Plasma thermal spraying method - Google Patents

Abstract

PURPOSE:To sufficiently melt and heat a thermal spraying material and to obtain a good thermally sprayed film by ejecting a plasma jet from an anode nozzle to heat and accelerate the particles of the thermal spraying material and generating high-frequency plasma by a coil in front of the anode nozzle. CONSTITUTION:Electricity is discharged by a DC power source 8 and a high-frequency generator 9 between a cathode 3 and the anode nozzle 2 to generate the plasma jet 14 of a working gas, such as Ar. The particles 16 of the thermal spraying material are introduced from a feed port 5 for the thermal spraying material powder and are heated and accelerated by the above-mentioned plasma jet 14 by which the particles are thermally sprayed to a surface 1a to be thermally sprayed of a work 1. An insulating cylinder 10 and the high-frequency impressing coil 11 wound on the outer periphery thereof are disposed in front of the anode nozzle 2 in the above-mentioned plasma thermal spraying method. The high-frequency plasma 15 is generated in the insulating cylinder 10 by the above-mentioned coil 11 and the high-frequency oscillator 13 while the above mentioned plasma jet 14 is ejected. The particles 16 of the above-mentioned thermal spraying material are sufficiently melted and heated in this way and the defectless thermally sprayed film which does not contain the unmolten particles is formed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a plasma spraying method.

[Conventional technology]

A conventional plasma spraying method will be explained with reference to a schematic diagram in FIG. First, as for the apparatus configuration, 1 is an object to be thermally sprayed, and 1a is its surface to be thermally sprayed. 2 is an anode nozzle of the plasma spray gun facing the surface 1a to be thermally sprayed, and is cooled by a cooling water passage 2a; 3 is a cathode whose tip is inserted into the anode nozzle 2; electrically isolated by 5 is a thermal spray material powder supply port bored in the side of the anode nozzle 2, and 6 is the powder supply port 1 to . 7 is a working gas supply port provided in the insulator 4; 8 is a DC power supply connected to the anode nozzle 2 and the cathode 3; and 9 is a high frequency generator connected in parallel with the DC power supply 8.

To perform plasma spraying using such a device, first supply gas A as the working gas into the anode nozzle 2 from the working gas supply lower, turn on the DC power supply 8, and close the space between the anode nozzle 2 and the cathode 3. A load voltage is applied.Then, when the high frequency generator 9 is turned on to generate an arc discharge between the anode nozzle 2 and the cathode 3, a continuous arc is generated by the power from the DC power supply 8, and the working gas becomes plasma gas. As a result, a high-temperature plasma jet 14 is ejected from the anode nozzle 2.

Next, when the thermal spray material powder from a powder supply device (not shown) is supplied from the powder supply boat 6 through the thermal spray material supply port 5 into the anode nozzle 2 using Ar gas, it is heated and accelerated by the plasma jet 14, and is heated at high temperature and high speed. Thermal spray material particles 1
6 and fly toward the sprayed surface 1a, collide with and adhere to the sprayed surface 1a, and form a sprayed coating. Note that during plasma spraying, water is forced to flow through the cooling water passage 2a in order to prevent the temperature of the anode nozzle 2 from rising.

However, in plasma spraying using direct current arc discharge, the plasma flow is at a high speed of several hundred m/s and the high temperature region of the plasma is narrow, so the spray material particles supplied into the plasma jet are not completely melted. Shouldn't you cut it?
Or, there is a risk that it may be mixed into the thermal spray coating without being melted at all.
This causes a decrease in the density and adhesion of the sprayed coating.

In addition, the particles of the thermal spray material heated and accelerated by the plasma jet collide and adhere to the surface to be thermally sprayed to form a thermal spray coating.During the collision, the particles become flattened, but depending on the type and particle size of the thermal spray material, some of the particles may become flattened. may scatter, and there is a risk that these scattered particles may become defects that reduce the denseness and adhesion of the film.

[Problem to be solved by the invention]

The present invention was proposed in view of these circumstances, and
To provide a plasma spraying method in which thermal spraying material particles are sufficiently melted and heated to form a coating within a sprayed coating, and the plasma flow rate can be controlled to eliminate flying debris during adhesion and flattening. purpose.

[Means to solve the problem]

To this end, the present invention provides an insulated cylinder and a high-frequency application coil wound around its outer circumference in front of the anode nozzle, from which sprayed material particles heated and accelerated by a plasma jet caused by a discharge between the cathode and anode nozzles to which direct current is applied are ejected. A high-frequency plasma is generated within the insulating cylinder while ejecting a plasma jet from the anode nozzle.

[Effect]

In the method of the present invention, the thermal spray material particles supplied to the anode nozzle are heated and accelerated by the plasma jet generated from the anode nozzle, and are sufficiently molten by the wide high-temperature region of the high-frequency plasma, so that they remain unmelted in the thermal spray coating. Alternatively, it is possible to prevent particles in an incompletely melted state from being mixed in and obtain a sound thermal spray coating.

In addition, by adjusting the outputs applied to the plasma jet and high-frequency plasma, the plasma flow velocity can be controlled, thereby eliminating flying debris when molten particles adhere to the sprayed surface and flatten it. .

〔Example〕

An embodiment of the plasma spraying method of the present invention will be described with reference to a schematic diagram in FIG.

In FIG. 1, ■ is an object to be thermally sprayed, and 1a is its surface to be thermally sprayed. 2 is an anode nozzle of the plasma spray gun facing the surface 1a to be thermally sprayed, and is cooled by a cooling water passage 2a; 3 is a cathode whose tip is inserted into the anode nozzle 2; electrically isolated by 5 is a thermal spray material powder supply port drilled in the side of the anode nozzle 2, 6 is the powder supply port, 7 is a working gas supply port provided in the insulator 4, and 8 is the anode nozzle 2 and cathode 3.
9 is a high frequency generator connected in parallel with the DC power source 8.

10 is an insulating cylinder such as a water-cooled quartz tube arranged in front of the anode nozzle 2; 11 is a coil wound around the outer periphery of the insulating cylinder 10; 12 is a supply port for supplying working gas into the insulating cylinder 10; 13 is connected to the coil 11 and has a frequency of 4 MHz, for example.
14 is a plasma jet injected from the anode nozzle 2, 15 is a high-frequency plasma generated within the insulating cylinder 10, and 16 is a flying thermal spray material particle.

In such a device configuration, Ar 5127m1n is supplied as a working gas into the anode nozzle 2, a no-load voltage of about 40 mm is applied between the anode nozzle 2 to be cooled and the cathode 3, and the high frequency generator 9 is turned on, a plasma jet 14 is ejected from the anode nozzle 2. Next, from the working gas supply port 12, 507! /min, or Ar50ρ
While supplying a mixture of H2 or 02 at several F/min into the insulating cylinder 10, the high frequency oscillator 13 is activated and a 20 KW, 4 MHZO high frequency current is applied to the coil 11. An alternating magnetic field is generated, and high frequency plasma 15 is generated.

On the other hand, ZrO with a particle size distribution of 10 to 40 pm is used as a thermal spray material.
, -8% (wt) Y20g is supplied into the anode nozzle 2 from the powder supply port 6 through the thermal spray material powder supply port 5 at a rate of Log per minute using Ar gas from a powder supply device (not shown). .

In this way, the thermal spray material particles 16 are heated and accelerated by the plasma jet 14, and the high-frequency plasma 15 further promotes heating-f6 melting, so that the unmelted or incompletely melted particles become completely molten. The melted and flying spray material particles 16 adhere to the sprayed surface la to form a sprayed coating.

Note that by adjusting the output of the DC power supply 8 and the high-frequency oscillator 13, the flow of the plasma jet 14 and the high-frequency plasma 15 can be controlled, thereby controlling the kinetic energy of the spray material particles 16 to Surface 1a
It is possible to reduce scattering when it adheres to the surface.

In this manner, according to the method of the present invention, since the plasma jet 14 and the high-frequency plasma 15 are simultaneously generated during thermal spraying, the thermal spray material particles 16 that are not sufficiently heated or not heated at all by the plasma jet 14 are sufficiently heated by the high-frequency plasma 15. As a result, unmelted or incompletely melted particles can be prevented from entering the sprayed coating on the sprayed surface 1a, and a healthy sprayed coating can be obtained. Furthermore, by adjusting the outputs applied to the plasma jet 14 and the high-frequency plasma 15, the plasma flow velocity can be controlled, and it is possible to eliminate flying objects when molten particles adhere to the sprayed surface 1a and flatten it.

〔Effect of the invention〕

In short, according to the present invention, an insulated cylinder and a high-frequency application coil wrapped around the outer circumference of the anode nozzle are arranged in front of the anode nozzle, from which thermal spray material particles heated and accelerated by a plasma jet caused by a discharge between the cathode and anode nozzles to which direct current is applied are ejected. and
By generating high-frequency plasma in the insulating cylinder while ejecting a plasma jet from the anode nozzle, the thermal spray material particles can be sufficiently melted and heated to form a coating within the thermal spray coating, and the plasma flow rate can be increased. The present invention is of great industrial benefit because it provides a plasma spraying method that can be controlled and eliminate debris during deposit flattening.

[Brief explanation of the drawing]

FIG. F is a schematic diagram showing an embodiment of the plasma spraying method of the present invention, and FIG. 2 is a schematic diagram showing a conventional plasma spraying method. DESCRIPTION OF SYMBOLS 1... Object to be thermally sprayed, 1a... Surface to be thermally sprayed, 2... Anode nozzle, 2a... Cooling water passage, 3... Cathode, 4...
- Insulator, 5... Thermal spray material powder supply port, 6... Powder supply boat, 7... Working gas supply port, 8... DC power supply, 9... High frequency generator, 10... Insulating cylinder, 11
...Coil, 12...Working gas supply 1-1.13.
...High frequency oscillator, 14...Plasma jet, 15
...high frequency plasma, 16...sprayed material particles. Agent Patent Attorney Masa Tsukamoto

Claims (1)

[Claims] An insulated cylinder and a high frequency application coil wound around its outer periphery are disposed in front of the anode nozzle, from which the sprayed material particles heated and accelerated by the plasma jet caused by the discharge between the cathode and anode nozzles applied with direct current are ejected. A plasma spraying method characterized in that high-frequency plasma is generated within the insulating cylinder while ejecting a plasma jet from a nozzle.